This invention relates to wireless communications systems and, more particularly, to wireless communications between wireless terminals and base stations in a multiple access communications system.
In a wireless multiple access communication system, the wireless traffic channel resource, e.g., bandwidth and time interval, is shared by all the wireless terminals, i.e., mobile units, in a particular cell. Efficient allocation of this traffic channel resource is very important, as it directly impacts the utilization of the traffic channel resource and the quality of service perceived by individual wireless terminal users. One such wireless communications system is the Orthogonal Frequency Division Multiplexing (OFDM) based Spread Spectrum Multiple Access system.
In a traditional wireless system, the traffic channel resource is managed by use of rate allocation. In particular, a dedicated control channel is typically established between a base station and a particular wireless terminal. The base station then allocates to the wireless terminal a traffic channel having a prescribed transmission rate through control message exchange on the dedicated control channel. Once the transmission rate allocation is completed, the wireless terminal may use the allocated traffic channel for an indefinite duration. When the traffic requirement changes, the base station and the wireless terminal change the transmission rate of the traffic channel again through control message exchange. A problem with this control message based transmission rate allocation arrangement is that in general the control message exchange can take quite a significant amount of time to complete and, consequently, the traffic channel resource allocation process may be quite inefficient. Specifically, assume that control message exchange takes time T to be completed. Suppose that a traffic channel has already been assigned to a wireless terminal. Further assume that there is some idle interval during which the assigned wireless terminal has no traffic to be transmitted. Then, it is impossible to allow another wireless terminal to utilize the traffic channel resource in the idle interval that is less than T, thereby resulting in under utilization of the traffic channel resource. In another example, assume that xe2x80x9clowxe2x80x9d priority traffic has been transmitted for one wireless terminal, then when xe2x80x9chighxe2x80x9d priority traffic arrives for another wireless terminal, the base station has to change the traffic channel resource allocation from the wireless terminal having the low priority traffic to the wireless terminal having the arriving high priority traffic. Exchanging control messages to realize the required traffic channel allocation change introduces latency in transmission and/or reception of the high priority traffic, which is extremely undesirable.
These and other problems and limitations of prior known wireless communications system traffic channel resource allocation arrangements are overcome by managing the traffic channel resource utilizing traffic segment allocation. This is realized by partitioning the channel resource into an assignment channel and a traffic channel in a fixed manner. The assignment channel includes assignment segments and the traffic channel includes traffic segments. The traffic segment is the basic traffic channel resource unit used to transport traffic data and has a prescribed finite time interval and bandwidth. Each traffic segment is associated with a so-called assignment segment in a prescribed manner. One or more traffic segments may be associated with a particular assignment segment. A base station broadcasts via an assignment segment which wireless terminal is to use a particular traffic segment. This is realized by transmitting a simple identifier for the particular wireless terminal assigned to the particular traffic segment in the assignment segment. Then, each active wireless terminal monitors all of the received assignment segments to detect any traffic channel assignments. Once a wireless terminal detects its identifier in an assignment segment, it proceeds to receive/transmit the traffic data in the traffic segment associated with the assignment segment including the detected identifier.
Technical advantages of applicantsxe2x80x9d unique invention are that: no control message or other message exchange is required; the traffic channel resource can rapidly be assigned to different wireless terminal users based on their traffic needs and channel conditions; and resource scheduling can be realized in an extremely flexible manner.